Dark energy cosmological model with anisotropic fluid and time varying lambda in Kaluza-Klein metric

Abstract

In this paper, we have investigated the dark energy cosmological model in the presence of anisotropic fluid in Kaluza–Klein metric with generalized time-dependent lambda L=αH² + βS² (α, β are free parameters; H is Hubble parameter and S is normal scale factor). Considering the equation of state (EOS) p = wr for normal dimensions and p_ψ= (omega+delta)rho for the fifth dimension, exact solutions of Einstein field equations of the anisotropic model are obtained ( where p - the pressure for normal dimensions, p_ψ – the pressure of the fifth dimension, (rho) - density of the fluid, 'omega' - EOS parameter, and delta -skewness parameter). It is concluded that the universe at its early stage shows anisotropic behavior due to its finite value delta. The variations of 'omega' and 'delta'  demonstrate the evolution from radiation dominated early universe to a dark energy-dominated universe. We have also investigated dark energy density, pressure, and other physical parameters. The physical parameters are dependent on free parameters and power index factor n which relates the extra dimension scale factor to the normal scale factor.